Insights into molecular structural changes of kerogen during thermal evolution investigated by advanced solid-state NMR spectroscopy Jingdong Mao Department of Chemistry and Biochemistry, Old Dominion University, VA, 23508 Molecular structural changes of kerogen during thermal evolution are not well know. It is well known that aromaticity increases with increasing thermal maturity. The increases in aromaticity can be due to (a). Structure with increased aromatic core size at the expense of alkyls; (b). Structure with unchanged aromatic core size and decreased (degraded) alkyl fraction, and (c) Structure with increased aromatic core size and almost unchanged alkyl fraction. This scenario of structure with unchanged aromatic core size and decreased (degraded) alkyl fraction is most consistent with the experimental data of 1H-13C recoupled long-range dipolar dephasing.